Radar sensors, which are often used for detecting the surroundings in vehicles with modern driver assistance systems, are operated in the frequency band of 76-77 GHz, for example. Enhanced radar sensors may have an extended frequency range of 76 GHz to 81 GHz, for example. Advantages of this increased available bandwidth are, for example, an increased spatial separation capability or the option for operating the radar sensor in different ranges of the frequency band in order to avoid disturbances due to interference by other radar sensors in the immediate vicinity.
In conventional radar sensors, irradiation of electromagnetic waves as radar waves is generally achieved using so-called patch antennas in the microstrip line technology. In the simplest case, a rectangular metal-plated antenna element (also referred to as a patch element) is situated on a circuit board substrate material, suitable for high frequencies, at a defined distance from a ground surface situated below same. Substrates that are suitable for high frequencies are relatively complicated technically, and are often difficult to integrate into standardized manufacturing processes.
One-layer substrate assemblies are sometimes limited in the possible frequency bandwidth, and for the frequency band of 76 GHz to 81 GHz, for example, have only limited usability. Multilayer substrate assemblies, which include multiple substrate layers suitable for high frequencies with etched structures, are often technically complex and involve a high level of manufacturing effort.
German Patent Application No. DE 10 2012 201 367 A1 describes a microwave radar device that is designed as a module made up of multilayer multipolymer circuit boards which include a metal-plated layer that is situated between two layers made of polymer materials and used for shielding and for signal routing.
FIG. 6a shows a schematic illustration of an example of an antenna system from the related art, and FIG. 6b shows a schematic cross-sectional view of the example of the antenna system from the related art.
Basic elements of the example of the antenna system are a first patch element 3, which is situated on a substrate material 4 above a ground surface 5 and coupled to a second patch element 1, which is mounted on a second material 2.